The facial artery enters the face lateral to the mandible at the anterior border of the masseter and passes upward and forward on a tortuous course to the corner of the mouth, giving off the inferior labial artery branches, which supply the base of the flap and adjacent muscles. Although not dissected in this operation, the facial artery can be mobilized readily until it becomes fixed beneath the risorious and zygomaticus major muscles near the mouth. After giving off the superior labial artery deep to the latter muscle, a smaller main trunk passes on and through facial muscles to reach the inner canthus. No vessels enter the deep surface of the distal portion of the flap superiorly.

All named arteries are accompanied by one or more veins; most drain into the facial vein. The terminal branches of the facial nerve lie deep in the facial muscles and are not endangered by flap elevation superficial to the muscle, as recommended [see Operative Technique section]. Rich anastomoses between the facial vessels and the deep perforators of the infraorbital and transverse facial vessels further assure an abundant blood supply to and from the flap. Division of the facial artery at the level of the mandible, for example, during radical neck surgery, is not a limiting factor, primarily because of similar rich anastomoses between the facial, masseteric, and buccal vessels (6).